The present invention refers to a method for the compression of an electric audio signal which is produced in the process of recording the ambient noise by means of an electroacoustic transducer, more particularly a microphone. Furthermore, the invention also refers to a device for carrying out the method.
In the field of audience research, which also comprises the acoustic perception of other media such as e.g. television, recordings of the acoustic environment of a panelist in a survey are used, i.e. the so-called hearing samples. The storage of these hearing samples on portable magnetic tape recorders is disclosed in U.S. Pat. No. 5,023,929. The inconvenient of this method is that the tape recorder is relatively large although it is intended to be permanently carried by the participant.
Consequently, it would be preferable to integrate the hearing sample recorder or monitor in an appliance which is normally worn or at least less visible. Such a possibility, namely the integration into a wristwatch, is mentioned in EP-A-0 598 682 to the applicant, this application being hereby incorporated into the present specification.
However, the mentioned application does not indicate how the hearing samples can be stored in the extremely narrow space and with the very limited energy available in a wristwatch or a similarly inconspicuous appliance over a considerable period of time such as at least a week. Although the specification mentions the need of compression procedures, known methods only are indicated.